In the manufacture of tires, cord-reinforced fabric is an important element of the final manufactured tire. Production of the cord-reinforced fabric is usually performed in a continuous manufacturing procedure and it is desirable to achieve the most satisfactory and efficient tire, that the individual cords of the fabric be uniformly spaced and lie in a parallel relationship with respect to each other. Usually the cord fabric is ultimately calendered, that is bonded within a layer of rubber for subsequent fabrication of the final tire. It is desirable that the manufacturing process of the cord fabric, either calendered or uncalendered, be within specified limits, and that during the manufacturing, adjustments can be made to the process to correct deviations from the desired parameters. Such adjustments prevent a considerable amount of fabric from being produced before the corrections can be made resulting in an imperfect fabric and/or resulting scrap.
The use of light, including scanning laser beams, has been used to measure numerous properties of woven textiles. Photodetectors measure both transmitted light which has penetrated the fabric and reflective light to quantitatively assess fabric on such attributes as cord diameter, presence of globs of fibers, missing cords, weave density, weft angle and other fabric and cord characteristics. In certain of these prior methods a digital computer has been used to analyze the detector signals and issue reports on fabric inspected at a speed up to 30" per second. However, such prior art systems are very costly and complex. Other known systems use line scanned CCD arrays often having up to 1024 elements. If, for example, a lens is selected to image a width of three inches of 33 end/in. fabric, the resolution would be 0.003 inches. Since the cord-to-cord spacing is 0.033 this means the measurement uncertainty is 10%. If it is important to know the total number of cords in certain applications, it would be necessary to develop the facility to positively register the entrance of each cord into the field of view as well as the exit of each cord from the field of view during the scanning. Such computer programming and system components also are considerably complicated and expensive for most cord production fabrication and manufacturing facilities.
Other methods and apparatus for determining the spacing between cords in a fabric or other characteristics of types of fabrics and/or components used in the manufacture of tires are set forth in the following patents:
U.S. Pat. No. 3,511,293 discloses a method of analyzing a tire by x-ray in which the plies are formed of an essentially weftless fabric comprising a plurality of parallel cords bonded together by a coating of rubber. An x-ray photograph of the crown portion of the tire will reveal the bias angle that the respective cords make with the circumference about the crown. Tracer cords are positioned in one of the plies so that after the tire is cured the x-ray picture of the tire will indicate any change in distance between the two cords to determine whether the cords positioned below the tread portion of the tire are loose or tight.
U.S Pat. No. 3,648,164 discloses an apparatus for detecting variations in the spacing of a plurality of conductive strands which are imbedded within a rubber or plastic layer. The apparatus includes a transmitter for transmitting microwave radiation in the direction normal to the tire's sidewall. A crystal detector and horn receiver is positioned within the tire and as the tire side wall is moved between the transmitter and receiver, differences in cord spacing along the side wall give rise to readings on the receiver.
U.S. Pat. No. 3,847,485 discloses a device which is adapted to measure on a point-to-point basis the distance on a test surface from a predetermined reference plane. The apparatus includes a light source, such as a laser, which provides optical energy for a collimated beam which oscillates along an optical synthetic axis. A part of the beam passes through a beam splitter and is transmitted and focused by lens onto the front surface of a mirror. The beam then enters a second beam splitter and is focused by a lens for projecting onto a surface being measured. The mirror oscillates at a fixed frequency and the position of the lens is directly related to the test surface.
U.S. Pat. No. 3,852,600 discloses a plurality of x-ray detectors positioned precisely with respect to the center line of a tread stock in order to detect mislocation of steel reinforcements, belts, chafer strips and bead bundles by subjecting uncured rubber layers to x-ray radiation. The intensity of the x-rays passing through the tire section is measured and thus is capable of sensing the relative location of the reinforcements within the tire.
U.S. Pat. No. 3,918,816 discloses a method and apparatus for dimensional inspection of a tire. The apparatus includes dynamic measurements for determining structural imbalance as well as determining surface contour and profile for tread wear purposes. The apparatus uses a small laser beam which impinges upon the surface to obtain positional data relating to the surface. The laser is mounted on a laser scanning mechanism which is controlled by a motor and has a position monitor.
U.S. Pat. No. 4,004,693 discloses an apparatus for inspecting the disposition of reinforcing steel ply cords in pneumatic tires. The apparatus includes a conveyor for feeding tires to an entry mechanism and a radial cord distribution detection mechanism is mounted between a pair of beams. The mechanism is slideably movable along guide rods and when the detector passes over the steel ply cords a weak voltage is produced and is amplified. An output signal determines the cord distribution in the tire.
U.S. Pat. No. 4,015,651 discloses a tire cord coating system which uses x-ray analysis to count the number of regular cords between a pair of specially prepared spirally wrapped steel cords.
U.S. Pat. No. 4,475,815 discloses a method and apparatus for measuring the width of a selvage rubber portion. A parallel light is emitted from a light source such as a halogen lamp, and the intensity distribution of light reflected by a transfer roller and coating sheet is detected by a photodetector. The angle formed by the light emitted by the light source along a plane perpendicular to the axial line of the transferring roller is set within a predetermined range and the photodetector is arranged to receive scattered light from the transfer roller. The intensity of incident light to the light receiving elements correspond to the position of various cords in the strip being measured.
European Patent Application No. 0 228 147 discloses a system for determining the bias weight of cord reinforced tire fabric which uses two radiation sources. One of the sources determines the fractional area of the fabric not containing steel cords while the other is used to measure the average attenuation of radiation passing through the fabric. Both sources and their corresponding sensors are movably mounted on a pair of beams which extend across the width of the fabric web. The source sensor assemblies continuously scan across the fabric width so that information from the entire fabric area is obtained.
European Patent Application No. 0 239 689 discloses a system for measuring the open space between, and the ratio of open space to cord diameter, of cord reinforced tire fabric. An x-ray source and detector scan across the tire fabric as it is calendered providing a signal corresponding to each edge of a cord. A counter provides a time interval measurement of each open space as the x-ray source and detector scans the fabric.
Although certain of these prior art systems and apparatus do provide a means for measuring the spacing and/or location of cords within a fabric, the method and apparatus do not achieve the results and advantages of my invention in such a relatively simple, efficient and inexpensive manner as described below and as set forth in the appended claims.